The Third Generation Partnership Project (3GPP) has initiated the Long Term Evolution (LTE) program to bring new technology, new network architecture and configurations and new applications and services to wireless communication networks in order to provide improved spectral efficiency, reduced latency, faster user experiences and richer applications and services with less cost. One goal of the LTE program is to develop an E-UTRAN (Evolved Universal Terrestrial Radio Access Network).
When a wireless transmit receive unit (WTRU) makes uplink transmissions in an E-UTRAN during initial call establishment, and whenever there are no allocated dedicated channels or shared channels, the WTRU accesses the network by using a random access channel (RACH). WTRUs apply different backoff mechanisms before utilizing RACH resources. Backoff may be applied before each access attempt, including reattempts following access failure. A WTRU may identify an access class and read a system information block (SIB) which it uses to calculate its backoff delay. Further, the network may dynamically signal a probability factor in a SIB.
A WTRU may infer that reception of a preamble negative acknowledgement (NACK) signal indicates a failure due to a collision. A WTRU may also infer that no preamble response indicates a failure due to interference or poor signal-to-interference ratio (SIR). Based on this inference, the WTRU may alter a backoff value for retransmitting RACH preambles. However, the inference is not reliable. If detection of an overload condition versus a case of poor SIR can be improved, a better decision regarding a backoff factor can be made by the WTRU.